Automatic steering system with displacement limiting means



J. F. HOLLISTER AUTOMATIC STEERING SYSTEM WITH DISPLACEMENT LIMITINGMEANS Filed Jan. 7, 1949 Dec. 8, 1953 e m m H T s N N 1 e w I m N a r Ha F s E I M Y B m K8555 zoiumma $.53 Q

Patented Dec. 8, 1953 UHTE AUTOMATIG STEERING SYSTEM WITH DISBLAQEMENTLIMITING A S a corporation 'of Delaware T p esent in ent on r ates oautomat e i syst ms' or mob e c aft such as? airoi te craft, for exampe... hjdflmore pa t cularly to a system th i 'ree' inscharacter n whichthe ra f mo ment; of the s rface controlling th raf m y b au mati lly lmited to d fin e. and pr d termined' imi s Conventional automaticsteering systems generally utilize a course displacementfsig'nal deop ys m form of ma ne ic or yro om;- pass for operating af control surfacesuch as a rudder, ior example, to return the craft to a desired coursewhich is to be maintained by the craft. Course selector mechanisms arealso p o n su s tems y h ope at on' of which a displacement 'signal inaybe inserted into the system to turn'the craft to'a desired new coursewhich is to'be, maintained thereafter.

The present invention contemplates the pro Vision of a novelautomatic.steeringsystem for mpbile craft, such system incorporatingrudder limiting means which is automatically operable when thedisplacement signal exceeds a predetermined valueto overpower ruddercontrol by the displacement signal and to assume primalty' con,- trolthereof whereby th ef ective rudder range is limited to desired limits.

An object of the present invention, therefore, is to provide a novelautomatic steering system for mobile craft.

Another object. of the invention is to provide a novel automaticsteering system for mobile craft in whi spite o th "ma n tud cf hdisplacement signal, the efiective rudder range may be automaticallylimi'ted to predetermined limits of movement.

A further object of the invention is to provide a nov l automati pilotor s erin ,s siemsiqr a mobile craft, provided with a movable. ruddersurface thereon, embodying an auxiliary adiustable signal generatorwhich is effective in response'to a predetermined value of adisplacement signal for assuming primary control of the, rudder surfaceto thereby limit the efiiect ive glidder range and, which, moreover, is'made inefiec-s. tive when the displacement signal drops below thepredetermined value" so that primarycontrel o th udd r bythedismacen entsignai reinstated.

Another object is to provide an automatically operable rudder limitingmechanism in an auto.- mati ee systemlfor m b le jcr t by virtu of whichd hd fle tiori, islh l'd' to iire eten mined limits in spite cf'themagnitude ofa disl m t sne 'norm ll lo v, ti t he. rudder.

s 1949, Serial No. ,7 29 clai (01. 318-489) The. above and iurther objcts and novel tea.- tures of the inventiofiwill more fullfappear fromthe following detailed description when the same is read in connejc onwith the'accompanying drawing. It is to be expressly understood,however, that the drawing is for the purpose of illustration only and isnot intended as a' definition of the limits 'of the invention;

The single figure of the drawing is a diagrammatic illustration of anovel automatic steering system for mobile craft embodying'the rudderlimiting means hereof.

Referring now to the drawing for a more detailed description of thepresent invention, the latter is there shown as en bodiedin aautomaticsteering system ge erally comprising a, reference or directionmaintaining means in'the form of a compass", generally designated withthe reference character 10, which may be a mag; netic, earth'inductorpr' a gyro compass. The compass is connected to a masterdirectionindicator II which includes, as better shown in copendingapplication ger'ial No. 516,488, filed December 31, 1943; now 1 tent'Number 2,625,348 and assigned to the 'ass'ign'ee of the prs ent in vention,an inductive coupling device having an angularly movable rotor and a twophase driving motora shift embod ing he novel system hereof,isdisplacedfrom a given course, a signal is generated by compass lflwhich is reproduced in the rotor" 9; the coupling device to therebyenergize the motor which will notonly displ c t t r to a nul nc tio u alo by way of a suitab e sha t 1 will an ulary is ac the wound r or 36inductiv na senerator a m tt r device ,;4- re ative to its wound statorI5. I

By displacement oi rotor is relative to its stator I5, the rotor beingenergized from SQ'SlliQ-e able source of current, signals are induced inthe stator wind n SWh-ichare communicated by way of leads It toawound-stator H-ofan in-. duct ce 8 havi g an ensula ly disp ac ablewound rotor 9 filhe resultant: flux-vector at stator I!resultingi-rom'the signals in the windings thereof induces 'gnal inwound rot-er w e ro, sto' si ns-1' atd c l4 and, therefore, i's'th'esame as-the signal devele opedby the compass." i The displacement signalthus developed by rotor l 9 isn'ormally fedfin'a manner to presentlyappear, by way oi leads 20' and 2;! across a vari able resistgr 22located at the input of a conventional rudder eha el amplifi" Anadi tebe ontact. 24

communicate the displacement signal to the first amplification stage or"the amplifier, such amplifier being more fully shown and described inthe aforementioned copending application. Amplifier output iscommunicated by way of a suitable cable 25 to the variable phase of atwo phase induction motor, generally illustrated as rudder servo 26which, assuming a clutch 21 to be engaged, displaces a rudder surface 28in accordance with the displacement signal.

Operation of motor 2% to displace rudder 28 also angularly displaces byway of a suitable shaft 29 a wound rotor at, energized from a suitablesource, relative to a wound stator 35 of an inductive follow-up device32. Displacement of rotor 3-!) relative to the stator develops aresultant signal in the latter which is applied across a resistor 33 atthe amplifier input by way of 183K151 34. One end of the resistor isgrounded as shown. the other end being engaged by an adjustable tap 35which, in turn, connects with one end of a third resistor 36, the latterbeing engaged an adjustable tap 3'! connected with one end of resistor22. The follow-up signal developed by device 32 is in series opposedrelation to the displacement signal, whose phase determines thedirection of servo operation, and builds up until it is equal andopposite to the displacement signal at which time motor is de-energized.As the craft is caused to return to its course the displacement signaldrops toward zero so that the follow up signal prevails to reverse motoroperation to center the rudder as the craft attains the desired courseat which time the follow-up signal drops to zero and the servomotor isagain ole-energized.

In addition to the displacement and follow-up signals, motor 25 is alsooperated by a signal representing a rate of turn function of the craftdisplacement. To this end, a rate gyro, generally designated with thereference character 38, displaces by way of a trunnion or shaft thewound rotor it of an inductive rate signal device 4| relative to itswound stator 2. The rotor 40, being energized by a suitable source ofcurrent, develops on displacement a resultant signal within the statorwhich is communicated by way of leads 53 and l t, in a manner topresently appear, to the amplifier input across resistor -36. The ratesignal impressed across resistor is in series with the displacement andfollow-up signals and as the craft departs from its course, the ratesignal adds with the displacement signal and opposes the follow-upsignal while on craft return to course the rate signal reverses to addwith the follow-up signal and opposes the diminishing displacementsignal in a well known manner.

In order that the craft course may be changed at vwill at a point remotefrom compass H3 and independently-thereof a course selector mechanism isprovided including inductive device I 8, the rotor of which is angularlydisplaceable relative to its stator by suitable means such as a knob 45.With the foregoing arrangement when it is desired to change craftcourse, knob 45 is manipulated an angular amount corresponding to theangular amount of course change desired. With the craft on a givencourse no signal is induced within wound rotor I!) so that the latterbears a null position relative to the resultant flux vector at stator I?or, stated in another manner, a position of synchronismis maintained byboth inductive devices I 4 and it. As soon, however, as knob 45 ismanipulated, rotor is is displaced from its null position so thatsynchronism is destroyed and an error or displacement signal is induced.therein which, through amplifier 23, operates rudder 28 to turn thecraft to the new course. As the craft attains its new and pre-set coursethe compass causes a signal to be developed within stator 55 of deviceIii which, as the pre-set course is achieved, becomes equal and oppositeto the displacement si nal set in by knob so that the latter signal iseliminated whereupon motor 2t becomes die-energized.

It has been discovered that with the use of the automatic steeringsystem above described on water craft, rudder displacement resultingfrom a given displacement signal may be greater than feasible foreffective operation of the system and for that reason the novel rudderlimiting means hereof is provided so that in spite of the magnitude ofthe displacement signal, rudder range may be effectively limited todefinite and desirable limits.

In accordance-with the present invention, the novel rudder limitingmeans hereof comprises a limit amplifier and discriminator unit,generally designated with the reference character 46, the output ofwhich, depending upon the phase of the displacement signal introduced atthe input of the unit, will energize one or the other of coils 4:! or 48or" a pair of relays 49 and 50. Energization of one or the other of therelays will disconnect the course selector mechanism and itsdisplacement signal as well as the rate signal of device 4| from theinput of amplifier 23 and in its stead connect to the amplifier inputthe output of an inductive auxiliary signal device 5|. The manner inwhich the displacement signal, when it has attained a predeterminedvalue, is automatically overpowered and a pre-set and fixed signalintroduced into the system to limit rudder deflection will now beconsidered.

The displacement signal developed in rotor i9, either because ofoperation of knob 45 or because of a craft departure from apredetermined course, is normally communicated not only to the amplifierinput by ways of leads 2G and 2! but is also communicated by way ofleads 52 to the primary 53 of a transformer 54 located at the input ofunit 46. Suitable adjustment devices for the signal may be provided inthe form of resistors 55, 56 and adjustable taps 5?, 58, respectively,as shown. A center tapped secondary 59 of the transformer connects withgrids 60 and BI of an amplifier and discriminator tube $2, current flowbeing effected at either plate 63 or c4 of the tube depending upon thephase of the incoming displacement signal. Plate 63 of tube 62 connectsby way of a lead 55 with the grid 66 of a firing tube 67 while plate 8dof tube 62 connects by way of a lead 68 with the grid 69 of asecondfiring tube 10. Tubes 6? and NJ are provided with biasing resistors l!and '12 which are so biased that neither of the tubes will be conductiveuntil the incoming displacement signal, manifested by current flow ateither of plate elements 63 or 64 of tube 62, exceeds a predeterminedvalue. As soon as the displacement signal exceeds the prescribed value,and depending upon the phase of such signal, current flow will occur ateither plate 13 of tube 61 or plate 14 of tube 70, the former plateconnecting by way of a lead 15 with relay coil 47 and the latterconnecting by way of a lead 16 with relay coil 48.

Assuming current flow at plate 13 of tube 61 relay coil 47 is energizedto thereby operate a bank of movable armatures 17, 78, 19 and out of"engagementwit'h fixed contacts 8|, 82,

93' and t lywith which. the armatures are no mally en aged, i, e2. whencoil. 4 is tie-en rgized, n enga ment with. spa ed fixe ontac s 8.5. 85.a1 and 8.8-. Contact 8! is conn cted with l A4, of the inductive ra edevice 4i whil fix d contact 82 is connected with lead 2! c n t d withrotor l9. Fix d contac 83 nd 84 a W l as contacts 85 and 86 are open cntacts- Movable armature ll is electrical y e t d with a movable armatue 89 oi a econd bank of movable armatures so, 9| and 92 of. relay.Armature 89 norm ly n ges with. a fixed n tact 93 which connects by wayor a lead at with one end of. resistor 35. In t s m nn r the rate s gnalof device 4! is normally impressed across resistor 36 at the amplifierinput.

Movable armature I8. on the other hand is electrically connected ithmovable armature as Which normally engages with a fixed contact 95connected by way or a lead 96 with one end of displacement signalresistor 22 by virtue of which the displacement signal of rotor I 9 isnor m ally impressed across resistor 22 at the amplino]: input. Movablearmature I9 is electrically connected by way of a lead 31 with movablearmature 92 which normally engages with an open contact 98 and movablearmature 80 is electrically connected by way of a lead 99 with movablearmature 9| which normally engages with an openfixed contact I00.

Upon energization of coil 48, movable armat llfis 89, 90, 9| and 92disengage contacts 33, 95, I and 98 and are brought into engagement withfixed spaced contacts IeI, H32, I03 and Hi l,

contacts I GI and I02 being open contacts while contact I03 connectswith contact 81 by way or 'a lead I and contact Its-connects withcontact 88 by way of a. lead I06. Contact I433 also connects by way of alead [01 with displacement signal lead 20 while contact I04 connectswith lead 96 associated with resistor 22.

Auxiliary signal generator device 5I comprises an angularly displaceablewound rotor [03 which is energized from a suitable source of current andis provided with a settable knob I09. Rotor I08 is inductively coupledwith wound stator I lo across which is interposed a resistor IIIengageable by an adjustable tap H2. One end of the resistor connects byway of a lead I13 with lead 199 interconnecting armatures 89 and 9!while tap II 2 is connected by way of a lead lid with lead 91 whichinterconnects armatures I9 and 92.

By manipulating knob I 69, rotor I88 may be displaced to any desiredamount so that a signal will be available across leads H3 and H4 whichwill limit, when the auxiliary generator is connected to the amplifierinput, rudder deflection in either direction to a predetermined anddefinite amount.

The operation of the novel automatic steering system hereof will now beapparent to those skilled in the art. During normal operation, i. e.,.vvith relays 4e and 56 .de-energized and with the displacement signalappearing at rotor I9 having a value below the predetermined value abovewhich one or the other of the relays will be energized, the displacementsignal will be applied across resistor 22 at one of its ends by lead 23and at its other end by way of lead 2|, fixed contact 82, movablearmatures' i8 and 9D, fixed contact 5 and lead 56. The displacementsignal is also communicated by way of leads 52 to the input of unit es,the value of the incoming signal, however, being such that neither oftubes 6! or In is conductive so that both rela s 49 and 50. remaintie-energized.

Inaddition to the displacement and follow-up signals the rate signal isalso normally applied at the input of amplifier 23 in series with thetwo first signals by virtue of lead 43 which connects stator 62 with oneend of resistor 35, and lead 44, fixed contact 8|, movable armatures I7and 89, fixed contact 53 and lead 9a which connect stator 52 with theother end of resistor 36. The three signals add algebraically at theamplifier input to control rudder movement as hereinabove described.

As soon as the displacement signal of rotor l9 exceeds the predeterminedvalue and depending upon the phase of such signal either tube 61 or 0becomes conductive to energize either relay 49 or so to disconnect thesource selector mech- EllllSlll and the rate signal generator fromamplifier 23 and to connect in their stead the output of auxiliarysignal generator 5i to the amplifier input for limiting control of therudder.

Assuming current fiow to occur at plate element '63 of tube 575, relaycoil M is energized to disengage armatures ll, 18, 79 and 89 from fixedcontacts 8|, 52, 8-3 and 8t and to bring them into engagement with fixedcontacts 85, 86 81 and 88. By disengaging armature I! from contact BIand armature 18 from contact 82 both the rate and the displacementsignals are disconnected from the input of amplifier '23. By bringingarmature 79 into engagement with contact 8'! and armature with contact8%, the signal of auxiliary generator bl is impressed across resistor 22of amp fier 23 y way of leads to and Iill the pha of auxiliary si nalenerator b ing the same as the phase 0 the displacement signal at rotoris. auxiliary sisnalso inserted controls ruddel' until such tilheasthedisnlacement si nal of rotor it drops below the predetermined valueat whi h time tube c1, ceases to conduct and relay is. deenersiz dwhereupon the auxiliary signal en r tor is disconnected from theamplifier in put and the course selectormechaniszn and rate signalgenerator are 're connected to the amplifier to take over control oftherudder.

Assuming, on the other hand, current flow to occur at plate element idoltube It, relay coil it is ener ized to disengage armatures afll Bil, iiiand 92 from ed contacts 95, Hill and 98 and-to bring them intoengagement with fixed contacts lili, 592, it and EM. By disengagingarmature 3.9 from contact stand armature as from contact the rate signalgenerator and the COHISESQ-r lector mechanism are again disconnectedfrom the amplifier input. By bringing armature ill into engagement withcontact Hi3 and armature 92 into engagement withcontact Hid, the outputof auxiliary generator'fil is again placedacross resistor 22 0f theamplifier input but ina reversed sense to that whenit is connected tothe ampli fier by energizat-ionof relay .45.. Once the. dis placementsignal of rotor IS dropsbelow thepredetermined value, tube ill ceasesto.conduct and relay 50 is die-energized whereupon the auxiliary signalgenerator isdisconnected from the amplifier and the courseselectormechanism and the rate si nal generator are again reconnected tothe amplifier to take overprimary control of the rudder.

It will now be apparent tothosc skilled in the art that a novelautomatic steering system for mobile craft ha been provided hereby withthe use of whichrudder deflection may be limited to a desired rangenotwithstanding the magnitude of a controlling displacement signal, suchcontrol being accomplished by the use of rudder limitin means which isautomatically effective to control rudder when the primary displacementsignal exceeds a predetermined value and is made ineffective when thedisplacement signal drops below the prescribed value and normal rudderoperation is reinstated.

Although but a single embodiment of the present invention has beenillustrated and described in detail, it is to be expressly understoodthat the invention is not limited thereto. Various changes may be madein the design and arrangement of the parts without departing from thespirit and scope of the invention as the same will now be understood bythose skilled in the art.

What is claimed is:

1. An automatic steering system for a mobile craft having a displaoeablecontrol surface thereon, said system comprising a servo motor adaptedfor connection to said surface for the operation thereof, positionmaintaining means for generating a signal when said craft departs from apredetermined position and normally connected to said motor forenergizing the latter, and surface displacement limiting means connectedto said position maintaining means and responsive to a predeterminedvalue of said signal for disconnecting said position maintaining meansfrom said motor, said surface displacement limiting means being normallydisconnected from said motor but adapted for connection thereto inresponse to the predetermined value of said signal for assuming primarycontrol of said motor.

2. An automatic steering system for a mobile craft having a movablerudder surface thereon, said system comprising a servo motor adapted forconnection to said rudder for the operation thereof, directionmaintaining means for generating a signal when said craft departs from apredetermined course and normally connected to said motor for energizingthe latter, rudder limiting means connected to said directionmaintaining means and adapted for operating said motor independently ofsaid direction maintaining means, said rudder limiting means beingnormally disconnected from said motor, and means responsive to apredetermined value of said signal for disconnecting said directionmaintaining means from said motor and for connecting said rudderlimiting means to said motor whereby the latter is under the primarycontrol of said rudder limiting means so long as said signal is at saidpredetermined value.

3. An automatic steering system for a mobile craft having a movablerudder surface thereon, said system comprising a servo motor adapted forconnection to said rudder for the operation thereof, directionmaintaining means for generating a signal when said craft departs from apredetermined course and normally connected to said motor for operatingthe later, means developing a rate of course change signal normallyconnected to said motor for combining with said first signal foroperating said motor, rudder limiting means connected to said directionmaintaining means and adapted for operating said motor independently ofsaid direction maintaining means and said rate of course change means,said rudder limiting means being normally disconnected from said motor,and means responsive to a predetermined value of said first signal fordisconnecting said direction maintaining means and said rate of coursechange means from said motor and for connecting said rudder limitingmeans to said motor whereby said motor is under the primary control ofsaid rudder limiting means so long as said signal is at saidpredetermined value.

4. An automatic steering system for a mobile craft having a movablerudder surface thereon, said system comprising a servo motor adapted forconnection to said rudder for the operation thereof, directionmaintaining means for generating a signal when said craft departs from apredetermined course and normally connected to said motor for operatingthe latter, means developing a rate of course change signal normallyconnected said said motor for combining with said first signal foroperating said motor, means responsive to the operation of said motorfor developing a follow-up signal for modifying operation of said motor,rudder limiting means for operating said motor independently of saiddirection maintaining means and said rate of course change means andnormally disconnected from said motor, and means responsive to apredetermined value of said first signal for disconnecting saiddirection maintaining means and said rate of course change means fromsaid motor and for connecting said rudder limiting means to said motor.

5. An automatic steering system for a mobile craft having a, movablecontrol surface thereon, said system comprising a servo motor adaptedfor connecting to said surface for operation thereof, positionmaintaining means for generating a signal when said craft departs from apredetermined position and normally connected to said motor forenergizing the latter, a second signal generator connected to saidposition maintaining means and adapted for operating said motorindependently of said position maintaining means, said second signalgenerator being normally disconnected from said motor, and meansresponsive to a predetermined value of said first signal fordisconnecting said position maintaining means from said motor and forconnecting said second signal generator to said motor.

6. An automatic steering system for a mobile craft having a movablerudder surface thereon, said system comprising a servo motor adapted forconnection to said surface for the operation thereof, directionmaintaining means for generating a signal when said craft departs from apredetermined course and normally connected to said motor for energizingthe latter, a second signal generator connected to said directionmaintaining means and adapted for operating said motor independently ofsaid direction maintaining means, said second signal generator beingnormally disconnected from said motor, and means comprising relay meansresponsive to a predetermined value of said first signal fordisconnecting said direction maintaining means from said motor and forconnecting said second signal generator to said motor.

'7. An automatic steering system for a mobile craft having a movablerudder surface thereon, said system comprising a servo motor adapted forconnection to said rudder for the operation thereof, directionmaintaining means comprising a first signal generator for developing adisplacement signal when said craft departs from a predetermined courseand normally connected to said motor for operating the latter to movesaid rudder to return said craft to said course, a second signalgenerator connected to said first signal generator adapted for manualsetting to develop a selected course signal and normally connected tosaid motor for operating the latter to move said rudder to turn saidcraft to said selected course, said second signal being effective tooperate said motor until said first signal generator develops a signalto eliminate said second signal, rudder limiting means responsive to apredetermined value of either of said signals for disconnecting saidsignal generators from said motor and for assuming primary control ofsaid motor.

8. An automatic steering system for a mobile craft having a movablerudder surface thereon, said system comprising a servo motor adapted forconnection to said rudder for the operation thereof, directionmaintaining means comprising a first signal generator for developing adisplacement signal when said craft departs from a predetermined courseand normally connected to said motor for operating the latter to movesaid rudder to return said craft 'to said course, a second signalgenerator connected to said first signal generator adapted for manualsetting to develop a selected course signal and normally connected tosaid motor for operating the latter to move said rudder to turn sa dcraft to said selected course, said second signal being effective tooperate said motor until said first signal generator develops a signalto eliminate said second signal, a third signal generator adapted forconnection to said motor for operating the latter independently of saidfirst two signal generators and normally disconnected from said motor,and means responsive to a predetermined value of either of said firsttwo signals for disconnecting said first two signal generators from saidmotor and for connecting said third signal generator to operate saidmotor.

9. An automatic steering system for a mobile craft having a movablerudder surface thereon, said system comprising a servo motor adapted forconnection to said rudder for the operation thereof, directionmaintaining means comprising a first signal generator for developing adisplacement signal when said craft departs from a predetermined courseand normally connected to said motor for operat ng the latter to movesaid rudder to return said craft to said course, a second signalgenerator connected to said first signal generator adapted for manualsetting to de- 'velop a selected course signal and normally connected tosaid motor for operating the latter to move said rudder to turn saidcraft to said selected course, said second signal being effective tooperate said motor until said first signal generator develops a signalto eliminate said second signal, a third signal generator adapted forconnection to motor for operating the latter independently of said firsttwo signal generators and normally disconnected from said motor, andmeans responsive to a predetermined value of either of said first twosignals and comprising relay means for disconnecting said first twosignal generators from said motor and for connect ing said third signalgenerator to operate said motor.

10. An automatic steering system for a mobile craf having a movablerudder surface thereon, said system comprising a servo motor adapted forconnection to said rudder for the operation thereof, directionmaintaining means comprising a first signal generator for developing adisplacement signal when said craft departs from a predeterm ned courseand normally connected to said motor for operating the latter to movesaid rudder to re .lIil said craft to said course, a second signalgenerator connected to said first signal generator adapted for manualsetting to develop a selected course signal and normally connected tosaid motor for operating the latter to move said 'rudderto turn saidcraft to said selected course, said second signal being effective tooperate said motor until said first signal genera tor develops a signalto eliminate said second signal, a third signal generator actuated inresponse to operation of said motor for modifying the operation of saidmotor, and rudder limiting means responsive to a predetermined value ofeither of "said first two signals for disconnecting said first twosignal generators from said motor and for assuming primary control ofsaid motor.

11. An automatic steering system for a mobile craft a movable controlsurface thereon, said system comprising a servo motor adapted forconnection to said surface for the operation thereof means comprising acourse selector mechanism normally connected to said motor and se'ttableto develop an energizing signal for said motor to actuate said surfaceto change the course of said craft, means operable by said -motor fordeveloping a second signal for modifying the operation of said motor,and means normally i said control surface.

disconnected from said motor but adaptedfor connection thereto inresponse to a predetermined value of said first signal for assumingprimary control of said motor to limit deflection of 12. Ah automaticsteering system for a inobile craft having movable control surfacethereon, said system comprising a servo motor adapted for connection tosaid surface for the operation 5 thereof, means comprising a positionselector mechanism normally connected to said motor and settable todevelop an energizing signal for said motor to actuate said surface tochange the position of said craft, means for developing a rate of changeof position signal normally connected to said motor for combining withsaid energizing signal for operating said motor, a third signalgenerator connected to said position selector mechanism being normallydisconnected from s aid motor but adapted for connection thereto forassuming primary control thereof, and means responsive to apredetermined value of said first signal for disconnecting said positionselector mechanism andsaid rate of change of position means from saidmotor and for onnecting said third signalgenerator to said motor.

13. An automatic steering system for a mobile craft having a movablecontrol surface thereon, said system comprising a servo motor adaptedfor y connection to said surface for the operation thereof, meanscomprising a position selector mechanism normally connected to saidmotor and settable to develop an energizing signal for said motor toactuate said surface to change the position of said craft, means fordeveloping a rate of change of position signal normally connected tosaid motor for combining with said energizing signal for operating saidmotor, means operable by said motor for developing a third signalformodifying the operation of said motor, a fourth signal generatornormally disconnected from said motor but adapted. for connectionthereto for as-- surning primary control thereof, and means responsiveto a predetermined value of said first signal for disconnecting saidposition selector mechanism and said rate of change of position meansfrom said motor and for connecting said fourth signalgenerator to saidmotor.

l t-In an automatic steering system for mo bile craft, the combinationWith a direction main- ?5 taming device and a remote adjustable meansfor changing course, of a pair of interconnected electrical signalgenerators adapted to produce a reversible signal upon loss ofsynchronism between the positions of said generators, a reversible servomotor operated from said signal in a direction to turn the craft in adirection to eliminate said signal, the rotor of one generator beingpositioned by the direction maintaining device and the rotor of theother generator being positionable by said adjustable means wherebycourse changes may be effected by adjustment of said remote adjustablemeans at a point remote from said direction maintaining device, andmeans responsive to a predetermined value of said signal foroverpowering said direction maintaining device and said remoteadjustable means and for assuming primary control of said servo motor.

15. In an automatic steering system for a mobile craft, the combinationwith a direction maintaining device and a remote adjustable means forchanging course, of a pair of interconnected electrical signalgenerators adapted to produce a reversible signal upon loss ofsynchronism between the positions of said generators, a reversible servomotor, means normally connecting said generators to said motor foroperating the latter by said signal in a direction to turn the craft ina direction to eliminate said signal, the rotor of one generator beingpositioned by the direction maintaining device and the rotor of theother generator being positionable by said adjustable means wherebycourse changes may be effected by adjustment of said remote adjustablemeans at a point remote from said direction maintaining device, a thirdsignal generator normally disconnected from said motor and adapted forconnection thereto for the operation thereof independently of said firstsignal, and means responsive to a predetermined value of said firstsignal for disconnecting said first two signal generators from saidmotor and for connecting said third signal generator to said motor.

16. An automatic steering system for a mobile craft having adisplaceable control surface thereon, said system comprising a servomotor adapted for connection to said surface for displacing the latter,an amplifier having an output connected to said motor and an input,position maintaining means for generating a signal when said craftdeparts from a predetermined position and normally connected with saidamplifier input for operating said motor, and means for limitingdisplacement of said surface connected to said po sition maintainingmeans, said displacement limiting means being normally disconnected fromsaid amplifier input but adapted for connection thereto for assumingprimary control of said motor, and means responsive to a predeterminedvalue of said signal for disconnecting said posi--- tion maintainingmeans from said amplifier input and for connecting said displacementlimiting means to said amplifier input.

17. An automatic steering system for a mobile craft having a movablecontrol surface thereon, said system comprising a servomotor adapted forconnection to said surface for the operation thereof, means comprising aposition selector mechanism normally connected to said motor andsettable to develop an energizing signal for said motor to actuate saidsurface to change the position of said craft, means comprising a sourceof con trol voltage normally disconnected from said motor but adaptedfor connection thereto to thereby confine m vement or said controlsurface is prescribed limits,and control means responsive tosaidenergizing signal and operative when the latter signal exceeds aprescribed value to make the position selector mechanism ineffective onsaid motor and to connect said source of control voltage to said motorto assume primary control of the latter.

18. An automatic steering system for a mobile craft having a movablerudder surface thereon, comprising a servomotor adapted for connectionto said rudder for the operation thereof, means comprising a courseselector mechanism normally connected to said motor and settable todevelop an energizing signal for said motor to actuate said rudder tochange the course of said craft, means comprising a source of controlvoltage normally disconnected from said motor but adapted for connectionthereto to thereby confine movement of said rudder to prescribed limits,and control means responsive to said energizing signal and operativewhen the latter signal exceeds a prescribed value to make the courseselector mechanism inefiective on said motor and to connect said sourceof control voltage to said motor to assume primarycontrol of the latter.

19. Anautomatic steering system for a mobile craft having a movablecontrol surf-ace thereon, said system comprising a servomotor adaptedfor connection to said surface for the operation thereof, meanscomprising a position selector mechanism normally connected to saidmotor and settable to develop an energizing signal of variable amplitudefor said motor to actuate said surface to change the position of saidcraft, limiting means comprising a source of control voltage having aprescribed amplitude normally disconnected from said motor but adaptedfor connection thereto to thereby confine movement of said surface toprescribed limits, and control means responsive to said energizingsignal and operative when the latter signal exceeds a prescribedamplitude to make the position selector mechanism ineffective on saidmotor and to connect said source of control voltage to said motor foroperating the latter.

20. An automatic steering system for a mobile craft having a movablerudder surface thereon, said system comprising a servomotor adapted forconnection to said rudder for the operation thereof, means comprising anangularly movable course selector normally connected to said motor andsettable to develop an energizing signal for said motor to actuate saidrudder to change the course of said craft, a manually operable knob foroperating said course selector, means comprising a source of controlvoltage normally disconnected from said motor but adapted for connectionthereto to thereby confine movement of said rudder surface to prescribedlimits, and control means responsive to said energizing signal andoperative when the latter signal exceeds a prescribed value to make thecourse selector ineffective on said motor and to connect said source ofcontrol voltage to said motor for operating the latter.

JAMES F. HOLLISTER.

References Cited in the file of this patent UNITED STATES PATENTS2,487,793 Esval .61; al, Nov. 15, 1949

